1. Field of Invention
The invention relates to a drilling apparatus, more particularly to a drilling apparatus which includes a chuck assembly for holding a drill bit and which chuck assembly includes a pawl and ratchet mechanism provided therein so that the chuck assembly does not require a chuck key when fixing the drill bit therein.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a drilling apparatus is shown to comprise a cylindrical chuck body (11) having an axial through bore (111) extending therethrough, which through bore (111) has a front portion to receive a section of an inserted drill bit (2) therein, an annular recess (113) with two opposed side walls formed on an external surface of the chuck body (11) and an outwardly extending flange formed on the chuck body (11) and having a front face which is flushed with the rear side wall of the annular recess (113). A pair of clamping units (12), which cooperatively define an enclosed clamp member, are rotatably provided on the annular recess (113). The enclosed clamp member has an engaging teeth (122) formed on the periphery thereof. The engaging teeth (122) are exposed when the enclosed clamp member is disposed in the annular recess (113). The enclosed clamp member (12) further includes an inclined inner wall provided with an internal screw thread (121) thereon. The enclosed clamp member (12) and the outwardly extending flange (16) and a section of the external surface of the chuck body (11) cooperatively define an annular clearance thereamong. The chuck body (11) further includes a retaining hole (112) formed therein adjacent to said enclosed clamp member and a plurality of through holes (114), each of said through holes (114) being inclined relative to the axial through bore (111) of the chuck body (11). The inclined through holes (114) pass through the outwardly extending flange (16), the annular clearance, the enclosed clamp member (12) and extend into the axial through bore (111) of the chuck body (11). A plurality of elongated clamping pieces (13) are received in a respective one of the through holes (114). Each of the clamping pieces (13) has an abutting side provided with a rack teeth (131), which meshes with internal thread (121) of the enclosed clamp member (12), and a clamping face (132), which is disposed in the axial through bore (111) adjacent to the drill bit (2). A retaining unit (14) is sleeved on the chuck body (11) and is securely connected to the enclosed clamp member (12).
When in use, the enclosed clamp member (12) is rotated by a chuck key (3). The chuck key (3) includes a positioning rod (31), which can be inserted into the retaining hole (112) of the chuck body (11), and a teethed wheel (32), which meshes with the engaging teeth (122) of the enclosed clamp member (12). When the chuck key (3) is rotated in a first direction, the enclosed clamp member (12) also rotates in the first direction, thereby moving the clamping pieces (13) interiorly of the axial bore (111) so as to clamp the drill bit (2). To release the drill bit, the enclosed clamp member (12) is rotated in a second direction opposite to the first direction, wherein the clamping pieces (13) moves exteriorly in the axial bore (111) of the chuck body (11).
Some drawbacks of the conventional drilling apparatus are as follow:
(1) Since there is no other means to prevent the enclosed clamp member (12) from rotating in the second direction, the drilling bit (2) may loosen due to the presence of a continuous vibrating action during the drilling operation.
(2) A chuck Key (3) is used to rotate the chuck body (11) so as to clamp the drill bit (2). The chuck key (3) may sometimes be misplaced, and without the chuck key (3), the chuck body (11) cannot be rotated.